Braid

ABSTRACT

It is provided that a braid which has high dimensional stability even in long-term high temperature storage and which fluctuates little in physical properties with the lapse of time. And it is provided that fishing lines, nets, ropes, and protective covers, and bulletproof materials using the same. A braid comprising a polyethylene fiber or polyethylene tape which has an intrinsic viscosity [η] of not less than 5.0 dL/g and not more than 30 dL/g and contains not less than 90% of ethylene as a repeating unit thereof, wherein a thermal shrinkage percentage is not less than 0.45% and not more than 8% under an environment of 80° C. for 240 hours.

TECHNICAL FIELD

The present invention relates to a braid which has high dimensionalstability even in long-term high temperature storage and use and whichfluctuates little in physical properties with the lapse of time. Moreparticularly, the invention relates to various kinds of interior cordsand nets such as blind cords, pleated cords, pleated screen door cords,curtain cords and shading screens, as well as concrete reinforcementmaterials, fishing lines, fenders, bulletproof materials, surgicalsutures, fastening filaments for meat, safety gloves, safety ropes,ropes for fishery industries, finishing ropes, mooring ropes, pullropes, archery chords, base materials for collecting organic andinorganic matters using the same.

BACKGROUND ART

A braid composed of multifilaments or monofilaments is used for varioususe applications such as fishing lines, blind cords and ropes. As abraid is diversified in use applications, the braid is required to havefunctionalities corresponding to the required characteristics ofproducts. For example, when a braid is used for a fishing line,filaments made of synthetic fibers such as polyamide fibers, polyesterfibers and polyolefin fibers and filaments made of fibers of metal suchas stainless steel, tungsten metal and amorphous metal have beenconventionally known as a general fishing line. A fishing line isrequired to have various characteristics depending on the kinds of fishfor catching and fishing methods, and in general, thin fishing lineshaving high strength are desirable. Accordingly, braids composed ofso-called ultra high molecular weight polyethylene fibers produced by agel-spinning method are used for providing fishing lines having highstrength and high elastic modulus (for example, see Patent Documents 1and 2). The fishing lines made of ultra high molecular weightpolyethylene fibers according to these inventions are fishing linesexcellent in high strength and high elastic modulus, but have theproblem that dimensional stability and physical characteristicsfluctuate along with practical use and the lapse of time. For example,there is the problem that if such fishing lines are used as a fishingline product for a long term, the braided fibers are gradually fastenedwith the lapse of use time to lose ductility, which is an importantfactor for fishing lines, and gradual hardening of the fishing linesgenerates a dimensional change and accordingly causes fluctuation ofphysical properties. As means for solving the problem, there isdisclosed a technique for producing a composite braid with othermaterials such as polyester monofilaments (for example, see PatentDocument 3). Dimensional stability is increased by making a braid to bea composite braid, but use of commonly used polyester fibers leads tolowering of strength and elastic modulus. As other means for solving theproblem, there is disclosed a technique for suppressing fluctuation ofphysical properties by, for example, performing a heat treatment afterprocessing into a braid, but in this case, when a braid is used as afishing line, there occurs not only the problem that the bundlingproperty of fibers constituting the braid is weak so that the fibersbraided are gradually fastened with the lapse of time, but also theproblem that the cross sectional shape becomes so flat as to increasethe friction with a fishing line guide and to lower wear resistance andthrowing characteristics (for example, see Patent Document 4).

On the other hand, as blind cords to be used for blinds moving up anddown, a braid has been conventionally used which is obtained by using atwisted yarn made of various kinds of synthetic fibers or natural fibersas a core yarn and coating the core yarn with a braided yarn made ofvarious kinds of fibers, but along with enlargement of blinds, aconventional product cannot be satisfactory for use. Accordingly, it isstrongly desired to produce cords more excellent in performance,particularly, in wear resistance. This kind of cord is used for blindsmoving up and down, and therefore, it is important that not onlydimensional change and untwisting are small even by repetitive use, butalso transmissibility for moving up and down operation, that is, astress at low strain is high. Further, it is also an important factorthat fluctuation such as expansion and contract corresponding to changeof environments including temperature and humidity is small for along-term.

In the conventional techniques, there is not only the problem relevantto long-term use of a product but also the problem relevant to productstorage. For example, there is the problem that physical propertieswhich a product originally has fluctuate when the product is stored fora long-term in a warehouse without air conditioning equipment or is putin environments having large temperature fluctuation for a long-termsuch as inside a carrier for product transport or inside a shipcontainer. The disclosed techniques described above cannot presentlysuppress dimensional change and fluctuation of physical properties withthe lapse of time not only during use of a product but also duringproduct storage.

PRIOR ART DOCUMENT Patent Documents

Patent Document 1: Japanese Examined Patent Publication Syo-60-47922

Patent Document 2: JP-A-Hei-3-244334

Patent Document 3 JP-A-2002-155456

Patent Document 4: JP-A-Hei-10-317289

SUMMERY OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to solve the above-mentionedconventional problems. The invention aims to provide a highly functionalbraid which has high dimensional stability and high physical propertyretention rate even in long-term use and storage and which is usable asfishing lines, nets, ropes, and protective covers by producing fibersthrough spinning and drawing steps, and not only properly controlling aformation step of the fibers but also precisely controlling tension at acooling step after the drawing step as well as tension at the time ofwinding after the cooling step, and further temperature and tension atthe time of a braid production of producing a braid using the fibers.

Solutions to the Problems

The inventors of the present invention have made earnest investigationson deformation conditions at the time of spinning and drawing in a solidstate, cooling conditions after the drawing step, winding conditions, aswell as not only temperature conditions and tension conditions in abraid production step for making a braid but also the structure,shrinkage percentage, thermal stress, stability of physical propertiesof a braid to be obtained, and have consequently completed the presentinvention.

The present invention has the following aspects.

1. A braid comprising a polyethylene fiber or polyethylene tape whichhas an intrinsic viscosity [η] of not less than 5.0 dL/g and not morethan 30 dL/g and contains not less than 90% of ethylene as a repeatingunit thereof, wherein a thermal shrinkage percentage is not less than0.45% and not more than 8% under an environment of 80° C. for 240 hours.

2. A braid comprising a polyethylene fiber or polyethylene tape whichhas an intrinsic viscosity [η] of not less than 5.0 dL/g and not morethan 30 dL/g and contains not less than 90% of ethylene as a repeatingunit thereof, wherein a tensile strength retention rate is not less than85% and not more than 115% under an environment of 80° C. for 240 hours.

3. The braid according to above 1 or 2, wherein a stress at the time of1% elongation is not less than 0.5 cN/dtex and not more than 20 cN/dtex.

4. The braid according to any one of above 1 to 3, wherein a shrinkagestress at not lower than 30° C. and not higher than 80° C. is not morethan 5.0 cN/dtex when measured by a thermo-mechanical analyzer (TMA).

5. The braid according to any one of above 1 to 4, wherein a loopstrength retention rate is not less than 15% when measured in accordancewith JIS L-1013.

6. The braid according to any one of above 1 to 5, wherein the braid isconstituted from not less than 3 fibers and at least one fiberconstituting the braid is a polyethylene fiber.

7. A braid constituted from at least one polyethylene fiber having anintrinsic viscosity [η] of not less than 5.0 dL/g and not more than 30dL/g, and comprising not less than 90% of ethylene as a repeating unitthereof, and having a storage modulus at not lower than 30° C. and nothigher than 80° C. of not less than 70 cN/dtex when measured by a solidviscoelasticity measurement apparatus after the braid is un-braided.

8. A braid constituted from at least one polyethylene fiber having anintrinsic viscosity [η] of not less than 5.0 dL/g and not more than 30dL/g, and comprising not less than 90% of ethylene as a repeating unitthereof, and having a shrinkage stress at not lower than 30° C. and nothigher than 80° C. of not more than 5.0 cN/dtex when measured by athermo-mechanical analyzer (TMA) after the braid is un-braided.

9. The braid according to any one of above 1 to 8, wherein a specificgravity is not less than 0.80 and not more than 2.0 and an averagetensile strength is not less than 8 cN/dtex and not more than 50cN/dtex.

10. The braid according to above 9, wherein the braid is colored.

11. The braid according to any one of above 1 to 10, wherein the braidis drawn at a draw ratio of not less than 1.05 times and not more than15.0 times at not higher than160° C. after braid production.

12. A fishing line using the braid according to any one of above 1 to11.

13. A rope using the braid according to any one of above 1 to 11.

14. A method for producing a braid, comprising

-   -   spinning a polyethylene which has an intrinsic viscosity [η] of        not less than 5.0 dL/g and not more than 30 dL/g and contains        not less than 90% of ethylene as a repeating unit thereof,    -   drawing the polyethylene at temperature of not lower than 80°        C.,    -   cooling the drawn filament at a cooling speed of not lower than        3° C./sec,    -   winding up the obtained drawn filament at a tension of 0.001 to        7 cN/dtex to prepare a polyethylene fiber,    -   twisting the polyethylene fiber if necessary, and    -   adjusting, in a subsequent braid production step, a time for        heating the polyethylene fiber constituting the braid to a        temperature of not lower than 70° C. to not longer than 30        minutes and a tension applied to the polyethylene fibers during        the heating to not less than 0.005 cN/dtex and not more than 15        cN/dtex.

Effect of the Invention

The braid of the present invention is characterized by having highdimensional stability and small fluctuation of physical properties forpractical use and with the lapse of time in a wide temperature range foruse as a product. The braid of the invention exhibits excellentperformance for use as fishing lines, various kinds of interior cordsand nets such as blind cords, pleated cords, pleated screen door cords,curtain chords and shading screens, all of which being required formoving up and down and opening and closing, fenders, surgical sutures,fastening filaments for meat, safety gloves, safety ropes, ropes forfishery industries, finishing ropes, archery chords, etc. The braid ofthe invention further exhibits excellent performance not only for use asthe above-mentioned molded products but also as base materials forcollecting organic and inorganic matters by making composites withvarious kinds of materials as well as water-retaining base materials,and the braid is thus widely usable.

Mode for Carrying Out the Invention

Hereinafter, the present invention will be described in detail. In apolyethylene fiber to be used for the braid, a tensile strength ispreferably not less than 13 cN/dtex. It is more preferably not less than20 cN/dtex and furthermore preferably not less than 25 cN/dtex. Theupper limit of the tensile strength is not particularly limited, but itis difficult to obtain a polyethylene fiber having a tensile strengthexceeding 60 cN/dtex in terms of technique and industrial production. Aninitial elastic modulus is preferably not less than 250 cN/dtex and notmore than 2300 cN/dtex. It is more preferably not less than 350 cN/dtexand furthermore preferably not less than 550 cN/dtex, and morepreferably not more than 1800 cN/dtex and furthermore preferably notmore than 1600 cN/dtex. If the polyethylene fiber has the tensilestrength and the initial elastic modulus as described above, breakagefrom an external force applied in a product processing step is hardlycaused. The measurement methods for the tensile strength and the initialmodulus will be described in detail in examples.

In a high strength polyethylene fiber constituting the braid of thepresent invention, an intrinsic viscosity is preferably 5.0 to 30 dL/g,more preferably 7.0 to 28 dL/g, and furthermore preferably 10 to 24dL/g. If the intrinsic viscosity is not more than 4.9 dL/g, a fibercannot be obtained which is excellent in dimensional stability, whichfluctuates little in physical properties with the lapse of time, andwhich has a tensile strength of not less than 10 cN/dtex. On the otherhand, if the intrinsic viscosity exceeds 30 dL/g, it is extremelydifficult for formation into a fibrous shape, and therefore it is notpreferable. If the intrinsic viscosity is not less than 5.0 dL/g,reduction of terminal groups of a polyethylene molecule leads toreduction of the number of structural defects in a product. As a result,physical properties such as tensile strength and elastic modulus andwear resistant performance can be improved.

The polyethylene preferably has a weight average molecular weight of notless than 700000 and not more than 8000000. It is more preferably notless than 800000 and not more than 7000000, and furthermore preferablynot less than 900000 and not more than 6000000. If the weight averagemolecular weight is less than 700000, in the case of being used in theform of a braid, not only the fiber tends to become fluffy due to localfriction, but also it becomes difficult to obtain the tensile strengthand the elastic modulus as described later as a braid, and therefore itis not preferable. On the other hand, if the weight average molecularweight exceeds 8000000, not only it becomes difficult to obtain afilament even by a solvent forming, which is a production method of thepresent invention, but also the obtained filament itself is not providedwith ductility so that a fishing line or the like made of a braid maylose flexibility and may give unpleasant feeling of use. As a method formeasuring a weight average molecular weight, a GPC measurement methodmay be generally employed for polyethylene having low molecular weight,but in the case of polyethylene having high weight average molecularweight as in the case of the present invention, the weight averagemolecular weight cannot be measured easily by the GPC measurement methodsince clogging or the like occurs in columns at the time of themeasurement. Accordingly, the weight average molecular weight can bemeasured based on the value of the intrinsic viscosity according to thefollowing equation disclosed in “Polymer Handbook Fourth Edition,Chapter 4, JOHN WILEY, 1999”.

Weight average molecular weight=5.365×10⁴×(intrinsic viscosity)^(1.37).

The high strength polyethylene fiber constituting the braid of thepresent invention substantially contains ethylene as a repeating unitthereof. Further, in a range in which effects of the present inventioncan be obtained, not only an ethylene homopolymer but also a copolymerof ethylene and a small amount of another monomer such as α-olefins,acrylic acid and derivatives thereof, methacrylic acid and derivativesthereof, and vinyl silane and derivatives thereof can be used. Thepolyethylene fiber may be the mixture of the copolymers, an ethylenehomopolymer and another copolymer, a blend of an ethylene homopolymerand a homopolymer such as other α-olefins. The polyethylene fiber maycontain a partial crosslinked structure. In addition, the polyethylenefiber may be a blend of polyethylenes having different weight averagemolecular weights such as a blend of high density polyethylene and ultrahigh molecular weight polyethylene, a blend of low density polyethyleneand ultra high molecular weight polyethylene, or a blend of low densitypolyethylene, high density polyethylene, and ultra high molecular weightpolyethylene as long as an intrinsic viscosity of the fiber measured bythe method described below satisfies the above-mentioned range. Thepolyethylene fiber may be a blend of two or more kinds of ultra highmolecular weight polyethylenes having different weight average molecularweights. Further, the polyethylene fiber may be a blend of polyethyleneshaving different molecular weight distributions as long as an intrinsicviscosity of the fiber measured by the method described below satisfiesthe above-mentioned range.

However, if the content of monomers other than ethylene is too high, itmay contrarily be an inhibition factor for drawing. Accordingly, interms of obtaining a high strength fiber, the content of another monomersuch as α-olefin is preferably not more than 5.0 mol %, more preferablynot more than 1.0 mol %, and furthermore preferably not more than 0.2mol % as a monomer unit. No need to say, an ethylene homopolymer may beused.

A method for producing a high strength polyethylene fiber constitutingthe braid of the present invention is not particularly limited, but asolvent forming method shown below is preferable. There are some methodsknown as the solvent forming method, and the solvent forming method isnot particularly limited, however, it is preferable to employ a solutionspinning method in which polyethylene is dissolved in a volatile organicsolvent such as decalin or tetralin or in a non-volatile solvent such asparaffin, the solvent serving as a solvent for polyethylene, and theresulting solution is formed into a fibrous shape. Besides the solventforming method, methods employable may be a melt extrusion method and amethod in which a film-like molded body obtained by compression formingat melting point or lower is split (cut) to be formed into a tape or afiber.

The solvent to be used at the time of producing the polyethylene fiberin the present invention is a solvent capable of dissolvingpolyethylene, and preferably a solvent having a boiling point not lowerthan the melting point of the polyethylene, and further preferably asolvent having a boiling point not lower than the melting point of thepolyethylene +20° C. Specific examples of the solvent include, inaddition to decalin, tetralin, and paraffin as described above,aliphatic hydrocarbon solvents such as n-nonane, n-decane, n-undecane,n-dodecane, n-tetradecane, n-octadecane, paraffin and kerosene; aromatichydrocarbon solvents such as xylene, naphthalene, tetralin,butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene,pentylbenzene, dodecylbenzene, bicyclohexyl, methylnaphthalene andethylnaphthalene, and their hydrogenated derivatives; halogenatedhydrocarbon solvents such as 1,1,2,2-tetrachloroethane,pentachloroethane, hexachloroethane, 1,2,3-trichloropropane,dichlorobenzene, 1,2,4-trichlorobenzene and bromobenzene; and mineraloils such as paraffin-based process oil, naphthene-based process oil andaromatic process oil. A paraffin wax to be used is not limitedparticularly to a compound composed only of carbon and hydrogen, and maycontain a small amount of oxygen and other elements. The paraffin waxcontains mainly a saturated aliphatic hydrocarbon compound, and specificexamples of the paraffin wax include n-alkanes having a carbon number ofnot less than 22 such as docosane, tricosane, tetracosane andtriacontane and mixtures containing mainly these components and lowern-alkanes; so-called paraffin waxes separated from petroleum, followedby refining; polyethylene waxes produced by a moderate/low pressuremethod, which are low molecular weight polymers obtained from ethyleneor by copolymerization of ethylene and another α-olefin; polyethylenewaxes produced by a high pressure method; ethylene copolymer waxes;waxes in which their molecular weights are reduced by thermallymodifying polyethylene such as polyethylene obtained by a moderate/lowpressure method or polyethylene obtained by a high pressure method;oxidized waxes such as oxides of these waxes and maleic acid-modifiedwaxes; and maleic acid-modified waxes.

At the time of dissolution, the concentration of polyethylene ispreferably not less than 0.5 wt % and not more than 40 wt %, morepreferably not less than 2.0 wt % and not more than 30 wt %, andfurthermore preferably not less than 4.0 wt % and not more than 20 wt %.If the concentration of polyethylene is less than 0.5 wt %, productionefficiency is extremely deteriorated, and therefore it is notpreferable. On the other hand, if the concentration of polyethyleneexceeds 40 wt %, discharging from nozzle as will be described belowbecomes difficult in a solvent spinning method due to extreme highmolecular weight, and therefore it is not preferable.

The highly functional polyethylene fiber constituting the braid of thepresent invention may be obtained by evenly dissolving theabove-mentioned polyethylene solution at a temperature higher than themelting point by not lower than 10° C., more preferably not lower than20° C., furthermore preferably not lower than 30° C. by using anextruder or the like, extruding the resulting solution, and supplyingthe solution to a spinning nozzle (spinneret) using a quantitativelysupplying apparatus.

Thereafter, the solution is discharged at not less than 0.1 g/min ofthrough put out of a nozzle orifice having a diameter of 0.2 to 3.5 mm,preferably 0.5 to 2.5 mm. Successively, the discharged molded body iscooled to 5 to 60° C. and thereafter wound at 800 m/min. In the stage ofspinning, it is preferable to adjust the temperature of the spinneret toa temperature higher than the melting point of polyethylene by not lowerthan 10° C. and the boiling point of the solvent employed. In atemperature range close to the melting point of polyethylene, theviscosity of the polymer is too high so that the molded body cannot bewound at high speed. On the other hand, if the temperature of thespinneret is adjusted to higher than the boiling point of the solventemployed, the solvent is boiled immediately after the solution isdischarged out of the spinneret so that filaments are often cutvertically below the spinneret, and therefore it is not preferable. Acooling method may be a dry quenching method using an inert gas such asair or nitrogen, or may be a cooling method using a miscible liquid oran immiscible liquid such as water.

The discharged gel filament is deformed at a magnification of not lessthan 1.1 times and not more than 100 times until the discharged gelfilament is completely thinned in the cooling step. The deformationmagnification is preferably not less than 2.0 times and not more than 80times, and more preferably not less than 5.0 times and not more than 50times. At that time, it is important to set the time required fordeformation to within 3 minutes. It is preferably within 2 minutes andmore preferably within in 1 minute. If the time required for deformationexceeds 3 minutes, the polyethylene molecular chains in the inside ofthe discharged gel filament are relaxed, and therefore not only a braidhaving high strength and high elastic modulus cannot be obtained butalso dimensional stability and high tensile strength or elastic modulus,which are characteristic properties of the braid of the presentinvention, are not compatible with each other. Consequently, it is notpossible to obtain a physical property retention rate which is small inchange with the lapse of time and which is desired for suchapplications, and therefore it is not preferable. In this case, aportion of the solvent may be removed from the discharged gel filamentduring the deformation process for the discharged gel filament.

An undrawn filament obtained through cooling is heated, and subjected todrawing several times while the solvent is removed, and may be subjectedto multistage drawing. Means for removing the solvent may be theabove-mentioned heating method in the case of using a volatile solvent,but may be a method for extracting the solvent using an extracting agentor the like in the case of using a non-volatile solvent. Examples of theextracting agent may include chloroform, benzene,trichlorotrifluoroethane (TCTFE), hexane, heptane, nonane, decane,ethanol and higher alcohol. A heat medium to be used in the drawing stepmay be an inert gas such as air or nitrogen, water vapor, a liquidmedium or the like, and the drawing may be carried out using heatingrollers. In this case, there is no need to carry out the solvent removalstep and the drawing step for the undrawn filament at the same time, andafter dried, the undrawn filament may be drawn in one or more stages. Noneed to say, the drawing may be carried out while removing the solvent.One important constituent for producing the braid of the presentinvention is a concentration of a residual solvent in the fiber beforethe braid production step. The concentration of a residual solvent ispreferably not less than 0.1 ppm and not more than 10000 ppm. Theconcentration is preferably not less than 1 ppm and not more than 8000ppm, and furthermore preferably not less than 10 ppm and not more than5000 ppm. If the concentration of a residual solvent in the fiberexceeds 10000 ppm, the time for relaxation of the molecular chains inthe fiber at the time of heating in the braid production step is toofast so that prescribed tension as will be described below cannot beobtained, and therefore it is not preferable. On the other hand, if itis less than 0.1 ppm, the time for relaxation of the molecular chains inthe fiber is slow and fastening of the fibers is insufficient at thetime of heating in the braid production step. This does not make itpossible to obtain a braid which has high dimensional stability andwhich fluctuate little in physical properties with the lapse of timeeven during long-term use, and therefore it is not preferable.

A method for drawing a polyethylene fiber constituting the braid of thepresent invention is one of important factors in the braid productionmethod of the present invention. The deformation speed at the time ofdrawing is preferably not less than 0.001⁻¹ and not more than 0.8 s⁻¹.It is more preferably not less than 0.01 s⁻¹ and not more than 0.1 s⁻¹.The deformation speed may be calculated from the draw ratio of thefiber, the draw speed, and the length of the draw interval. That is, thedeformation speed (s⁻¹)=(1−1/draw ratio) draw speed/length of drawinterval. If the deformation speed is too high, the fiber is brokenbefore a sufficient draw ratio is achieved, and therefore it is notpreferable. On the other hand, if the deformation speed of the fiber istoo slow, the molecular chains are relaxed during the drawing, and afiber having high physical properties cannot be obtained while beingmade thin by the drawing. As a result, when the fiber is formed into abraid, the tensile strength and the elastic modulus are lowered, andtherefore it is not preferable.

The draw ratio of the undrawn filament is recommended to be not lessthan 10 times and not more than 60 times, preferably not less than 12times and not more than 55 times, and furthermore preferably not lessthan 15 times and not more than 50 times, as a total draw ratio in bothcases of one stage drawing and multistage drawing. In the drawing step,the polyethylene fiber is drawn under conditions of a temperature nothigher than the melting point in one or more stages. When the drawing iscarried out a plurality of stages, it is preferable that the temperatureat the time of the drawing is higher as a later drawing stage. In thedrawing temperature in the last stage of the drawing, the temperature ofthe polyethylene fiber is not lower than 80° C. and not higher than 160°C., and preferably not lower than 90° C. and not higher than 158° C.Conditions for a heating apparatus may be set so as to give thetemperature to the polyethylene fiber at the time of the drawing. Inthis case, the filament temperature can be measured by using an infraredcamera (SC 640, manufactured by FLIR systems).

Further, one of important constituents of the present invention is amethod for drawing the undrawn filament in a solid state. As describedabove, not only the number of stages of drawing and the drawingtemperature are important but also a particularly important factor isthat the time required for deformation in a solid state is set to within30 minutes. The time is preferably within 15 minutes and more preferablywithin 10 minutes. If the time required for deformation exceeds 30minutes, the molecular chains in the inside of the fiber are relaxedeven if prescribed conditions are maintained at the time of productionas will be described below, so that the fibers cannot be fastened(shrunk) one another in the braid production step as a post-process, andtherefore it is not preferable. The deformation time in the case ofdrawing in multistage is the time at the time of drawing in the lateststep.

In the present invention, it is necessary not only for the bundlingproperty among the fibers to be high before the braid production step,but also for the molecular chains in the inside of the polyethylenefiber to keep high bundling property after the braid production step.That is, it is important that the degree of crystallization is kepthigh, and the orientation to the fiber axial direction is not relaxed.

It is consequently possible to improve the bundling property among thefibers constituting the braid to some extent by increasing the degree ofcrystallization or degree of crystal orientation of the fiber to acertain extent by heat treatment in the braid production step as will bedescribed below. However, if the degree of crystallization or the degreeof crystal orientation is extremely increased by heat treatment in thebraid production step, the fiber is shrunk significantly at the time ofthe heat treatment, and the braid is resultantly hard and therefore itis not preferable.

On the other hand, when conditions themselves are not proper such thatthe heat treatment after the braid production as will be described belowis carried out at a high temperature and/or the treatment time isprolonged as well as tension is low, the molecular chains in the fiberare relaxed and the physical property of the resulting braid,particularly the bundling property of the braid, is consequently toolow, and therefore it is not preferable.

An object of the present invention is to provide a braid whichfluctuates little in strength change with the lapse of time for along-term. As one of important factors of the present invention toaccomplish the object, the drawn filament heated to not lower than 80°C. is cooled to 50° C. at a cooling speed of preferably not lower than3° C./sec and not higher than 500° C./sec. The cooling speed is morepreferably not lower than 10° C./sec and not higher than 400° C./sec,and furthermore preferably not lower than 20° C./sec and not higher than300° C./sec. A residual strain caused at the time of drawing can beretained by cooling from the temperature at the time of drawing to 50°C. within a prescribed range of time. The temperature of 50° C. issufficiently lower than the crystal dispersion temperature of thepolyethylene fiber, and it is made possible to exhibit fastening of thefibers one another, which is important for the heat treatment in thebraid production step as will be described below, by setting thetemperature to not higher than 50° C. If the cooling speed for the drawnfilament is lower than 3° C./sec, the molecular chains of the fiber arerelaxed so that fastening among the fibers in the later braid productionstep become insufficient, and the braid to be obtained may havedeteriorated dimensional stability, and therefore it is not preferable.On the other hand, if the cooling speed of the drawn filament after thedrawing exceeds 500° C./sec, the residual strain in the drawn filamentbecomes too large after the cooling so that the braid after the braidproduction step may be consequently hard. Accordingly, the braid cannotbe used in applications such as fishing lines for which flexibility isrequired, and therefore it is not preferable. As a cooling method, awater bath having not higher than 50° C. is available. As other coolingmeans, a cooling method may be available which brings the fiber intocontact with a roller having a surface temperature of, for example, nothigher than 50° C. In this case, a plurality of rollers adjusted so asto have a lower surface temperature as set in the later step may be usedfor cooling the fiber. For example, when the cooling is carried out byusing three rollers each having different temperature, the fiber may becooled through the surface temperature of the roller immediately afterthe drawing being adjusted to 80° C., the surface temperature of thesecond roller to 60° C., and the surface temperature of the third rollerto 30° C. in this order. As other means, cold blow of air or an inertgas may be used and there is no particular limitation as long as theabove-mentioned cooling speed is satisfied.

As one of important factors of the present invention, the cooledfilament is wound up at a tension of preferably not less than 0.001cN/dtex and not more than 7.0 cN/dtex, and more preferably not less than0.05 cN/dtex and not more than 3.0 cN/dtex. It is made possible to windup the polyethylene fiber with a residual strain retained by winding upthe filament within the above-mentioned range. If the winding-up tensionis less than 0.001 N/dtex, the residual strain is lowered and it is notpreferable. On the other hand, if the winding-up tension is adjusted tomore than 7.0 cN/dtex, monofilament of the fiber tend to be cut easily,and therefore it is not preferable. The fiber temperature at the time ofwinding up is preferably not higher than 60° C. The fiber temperature ismore preferably not higher than 50° C., and furthermore preferably nothigher than 45° C. If the temperature at the time of winding up exceeds60° C., the residual strain fixed by the above-mentioned cooling step isrelaxed, and therefore it is not preferable.

The polyethylene fiber has a maximum value of thermal shrinkage stressof not less than 0.05 cN/dtex and not more than 5.0 cN/dtex, morepreferably not less than 0.10 cN/dtex and not more than 3.0 cN/dtex, andfurthermore preferably not less than 0.20 cN/dtex and not more than 1.0cN/dtex in the fiber state before processed into a braid. If the maximumvalue of thermal shrinkage stress is less than 0.05 cN/dtex, fasteningof the fibers one another is weak even by the heat treatment step at thetime of the braid production step, and it is not possible to keep stabletensile strength and elastic modulus in a wide range of temperature forproduct use, and therefore it is not preferable. On the other hand, ifthe maximum value of thermal stress exceeds 5.0 cN/dtex, the fibers areextremely strongly fastened one another and the bending rigidity isincreased at the time of the heat treatment in the braid productionstep, so that the braid becomes hard and tends to have significantunevenness of fineness in the longitudinal direction, and therefore itis not preferable. The phrase “unevenness of fineness in thelongitudinal direction” means CV % of fineness obtained by continuouslysampling every 1 m of a braid in the longitudinal direction at 10 timesand calculating the obtained each weight. The CV % is not more than 15%,preferably not more than 12%, and furthermore preferably not more than8%. The equation for calculating the CV % is as follows:

CV % (unevenness of fineness in longitudinal direction ofbraid)=100×(standard deviation of fineness)/(average value of fineness)

The temperature at which the maximum value of thermal shrinkage stressis indicated is preferably in a range of not lower than 80° C. and nothigher than 160° C. The temperature is more preferably not lower than85° C. and not higher than 150° C., and furthermore preferably not lowerthan 100° C. and not higher than 140° C. If the temperature at which themaximum value of thermal shrinkage stress is indicated is lower than 80°C., the time from the fiber production to the braid production becomeslong, dimensional change and fluctuation of physical properties may becaused in the fiber state, and therefore it is not preferable. On theother hand, if the temperature at which the maximum value of thermalshrinkage stress is indicated exceeds 160° C., the heat treatmenttemperature at the time of braid processing step is required to be highand the braid tends to be broken easily in the processing step, andtherefore it is not preferable.

The polyethylene fiber constituting a braid may be twisted, mixed withresin, or colored before processed into a braid or if necessary.

The braid of the present invention is preferable to be braided by notless than 3, that is, the braid is preferable to be constituted by notless than 3 fibers. If the number of the fiber is not more than 2, abraid-like shape cannot be formed and the contact surface area with aguide or the like is enlarged, so that the wear resistant performance isinferior and smoothness upon moving the braid is deteriorated. The braidof the present invention is required to have at least one high strengthpolyethylene fiber having physical properties of the present inventionas a fiber constituting the braid. Use of the high strength polyethylenefiber as a fiber constituting the braid makes it possible to keep highstrength and high elastic modulus and reduce the fluctuation ofdimensional stability and the fluctuation of physical properties withthe lapse of time. As long as at least one constituent fiber is a highstrength polyethylene fiber, other fibers constituting the braid may becomposited with fibers of other materials, for example, polyesterfibers, polyamide fibers, liquid crystal polyester fibers, polypropylenefibers, acrylic fibers, aramid fibers, metal fibers, inorganic fibers,natural fibers, or recycled fibers. The fibers other than one highstrength polyethylene fiber may be multifilaments, monofilaments,composites with short fibers, or split yarns produced by splittingtape-like or ribbon-like molded body of the polyethylene fiber itself.The single filament shape of each fiber may be circular or irregular, ormay be selected from hollow, flat shape, and the like. The respectivefibers may be partially or entirely colored or melt-bonded, and may bemixed with additives such as an antioxidant, a heat stabilizer, a flameretardant, a surfactant, a fluorescent brightening agent, a surfacereforming agent, an antibacterial agent, a corrosion inhibitor, awear-adjusting agent, an antistatic agent, a light-resistant stabilizer,an ultraviolet absorbent and a plasticizer, if necessary.

In the braid, a tensile strength is more preferably not less than 8cN/dtex and furthermore preferably not less than 20 cN/dtex. The upperlimit of the tensile strength is not particularly limited, but it isdifficult to obtain a braid having a tensile strength exceeding 50cN/dtex in terms of technique and industrial production. An initialelastic modulus is preferably not less than 150 cN/dtex and not morethan 1800 cN/dtex. It is more preferably not less than 250 cN/dtex andnot more than 1400 cN/dtex, and furthermore preferably not less than 350cN/dtex and not more than 1300 cN/dtex. If the braid has the tensilestrength and the initial elastic modulus as described above, changes inphysical properties and shape by external force are hardly caused at thetime of use as a product.

In the braid of the present invention, a stress at the time of 1%elongation is preferably not less than 0.5 cN/dtex and not more than 20cN/dtex. It is more preferably not less than 0.8 cN/dtex and not morethan 12 cN/dtex, and furthermore preferably not less than 1.0 cN/dtexand not more than 10 cN/dtex. If the stress at the time of 1% elongationis less than 0.5 cN/dtex, for example, when the braid is used for afishing line, a bite of fish cannot be transmitted to fingers, andtherefore it is not preferable. On the other hand, if the stress at thetime of 1% elongation exceeds 15 cN/dtex, for example, when the braid isused for a fishing line, even slight disturbance is transmitted asstress to fingers so that it is difficult to distinguish a bite of fishfrom noise, and therefore it is not preferable.

In a method for braiding a braid of the present invention, a braidingangle is 6 to 35°, preferably 15 to 30°, and more preferably 18 to 25°.If the braiding angle is less than 6°, the braid form becomes unstableand the cross section tends to be flat easily. Further, the stiffness ofthe braid is low, and accordingly the performance as a product issignificantly deteriorated. On the other hand, if the braiding angleexceeds 35°, the braid form is stabilized but the retention rate of thetensile force of a cord to the tensile force of an original filament islowered, and therefore it is not preferable. In the present invention,the braiding angle is not limited to the range from 6 to 35°.

The braid of the present invention is produced by braiding not less than3 fibers, but in the present invention, the number of the fiber is notparticularly limited, and a braid produced by braiding not less than 3and not more than 16 fibers is preferably used. As long as at least onepolyethylene fiber described above is contained in the constituentfibers and the physical properties of the braid satisfy theabove-mentioned ranges, the other constituent fibers may include longfibers, short fibers, or monofilaments of other materials. Examples ofthe other materials include not only organic fibers such as polyamidefibers, polyester fibers, liquid crystal polyester fibers, acrylicfibers and PBO fibers, but also metal fibers and inorganic fibers.

Further, one of important constituents of the present invention is apost-treatment method after the above-mentioned braid production step.Specifically, temperature, time, and tension at the time of subjectingthe braid underwent the above-mentioned braiding step to a heattreatment step, and also temperature and tension at the time of windingstep.

The heat treatment is carried out desirably at not lower than 70° C.,preferably at 90° C., and more preferably at 100° C. for not shorterthan 0.1 seconds and not longer than 30 minutes. The upper limit of thetreatment temperature is not higher than 160° C. If the temperature forthe heat treatment is lower than 70° C., it is close to the crystaldispersion temperature of the constituent polyethylene fiber, so thatthe fastening owing to the residual strain of the fiber becomesinsufficient, and therefore it is not preferable. On the other hand, ifthe heat treatment temperature exceeds 160° C., not only breakage(thermal cutting) of the braid tends to be caused easily, but also it isnot possible to obtain desired physical properties for the braid, andtherefore it is not preferable. The treatment time is preferably notshorter than 0.5 seconds and not longer than 25 minutes, and morepreferably not shorter than 1.0 second and not longer than 20 minutes.If the treatment time is shorter than 0.1 seconds, the fastening owingto the residual strain of the fiber becomes insufficient, and it is notpreferable. On the other hand, if the heat treatment time exceeds 30minutes, not only breakage of the braid tends to be caused easily, butalso it is not possible to obtain desired physical properties for thebraid, and therefore it is not preferable.

A tension applied to the braid at the time of heat treatment after thebraid production, which is an important factor in the present invention,is preferably not less than 0.005 cN/dtex and not more than 15 cN/dtex.It is more preferably not less than 0.01 cN/dtex and not more than 12cN/dtex, and furthermore preferably not less than 0.05 cN/dtex and notmore than 8 cN/dtex. In the heat treatment step, it is important thatthe three factors, that is, the treatment temperature, the treatmenttime and the treatment tension, are adjusted to within theabove-mentioned ranges in terms of obtaining the braid of the presentinvention. For example, if the tension during the treatment is higherthan the above-mentioned range, the braid is broken while passingthrough the heat treatment step, or the physical properties of the braidto be obtained are lowered, or dimensional stability is lowered, or thefluctuation of the physical properties with the lapse of time becomessignificant, and therefore it is not preferable.

A method for heat during heat treatment is not particularly limited. Forexample, hot water bath in which resin is dispersed or dissolved inwater, oil bath, hot roller, radiation panel, steam jet, a hot pin andthe like which are a known method are recommended, and the method is notlimited in these. After or during the braid processing step, the braidmay be twisted, mixed with resin, or colored if necessary. Further,during the heat treatment step, the braid may be subjected to re-drawingat a draw ratio of not less than 1.05 times and not more than 15 times.If the draw ratio in the re-drawing is less than 1.05 times, the braidis loosened in the heat treatment step, and therefore it is notpreferable. On the other hand, if the draw ratio in the re-drawingexceeds 15 times, breakage of the fiber constituting the braid occurs,and therefore it is not preferable.

It is important to wind up the braid of the present invention at atemperature lower than the crystal dispersion temperature of the fiberconstituting the braid by not lower than 5° C., preferably not lowerthan 10° C., and more preferably not lower than 20° C. If thetemperature for winding is equal to or higher than the crystaldispersion temperature, residual strain is generated inside a product tobe obtained, and dimensional change or fluctuation of physicalproperties is caused after making into a product, and therefore it isnot preferable. Further, the shrinkage stress in the range from aboutroom temperature to about crystal dispersion temperature of the fiberconstituting the braid as the used environment temperature of theproduct becomes high, changes in physical properties and dimension mayoccur depending on the environment change, and further the limitation iscaused such that the process condition of products and the usedtemperature range of the final products are restricted, and therefore itis not preferable. Specifically, it is preferable to wind up the braidat not higher than 50° C.

The braid of the present invention has a characteristic of smalldimensional change even at high temperature. The shrinkage stress in arange of not lower than 30° C. and not higher than 80° C. is preferablynot more than 5.0 cN/dtex, when measured by TMA. The shrinkage stress ismore preferably not more than 0.8 cN/dtex, and furthermore preferablynot less than 0.001 cN/dtex and not more than 0.7 cN/dtex. If theshrinkage stress exceeds 5.0 cN/dtex, the dimensional change becomessignificant.

The braid of the present invention has a characteristic of smalldimensional change even for long-term storage or long-term use.Specifically, the thermal shrinkage percentage is in a range from 0.45%to 8%, preferably not less than 0.5% and not more than 6.5%, and morepreferably not less than 0.55% and not more than 4% even for continuoususe under an environment of 80° C. for 240 hours. Accordingly, even whenstored in a warehouse or inside a carrier for a long-term, thedimensional stability can be retained.

The braid of the present invention shows good physical propertyretention rate, that is, small fluctuation of tensile strength with thelapse of time, for a long-term. Specifically, the tensile strengthretention rate is in a range from not less than 85% to 115%, preferablynot less than 88% and not more than 112%, and more preferably not lessthan 90% and not more than 110% even for continuous use under anenvironment of 80° C. for 240 hours. Consequently, the fluctuation ofthe performance of products according to the environment change can besmall in applications, as fiber-reinforced plastics,concrete-reinforcing fibers, ropes, and the like, in which a tensileforce is high and change of an ambient temperature is large in a usedstate.

In the braid of the present invention, the characteristics of at leastone polyethylene fiber constituting the braid are important in order toretain the dimensional stability and the physical property stabilizationwith the lapse of time as a braid after making into a product. It isbecause even if the above-mentioned braiding method for fiber is carriedout, it is difficult to produce a braid having the characteristics ofthe present invention unless at least one polyethylene fiberconstituting the braid has the following characteristics.

At least one polyethylene fiber constituting the braid product has astorage modulus of not less than 70 cN/dtex, preferably not less than 90cN/dtex, and more preferably not less than 110 cN/dtex at not lower than30° C. and not higher than 80° C., when measured by a solidviscoelasticity measurement apparatus after the polyethylene fiber isun-braided from the braid. If the storage modulus at not lower than 30°C. and not higher than 80° C. is less than 70 cN/dtex when measured by asolid viscoelasticity measurement apparatus after the polyethylene fiberis un-braided from the braid, the polyethylene fiber tends to beaffected easily by external force applied at the time of product use sothat dimensional change is caused during long-term product use, andtherefore it is not preferable. On the other hand, the upper limit ofthe storage modulus at not lower than 30° C. and not higher than 80° C.is not more than 1500 cN/dtex, preferably not more than 1200 cN/dtex,and more preferably not more than 1000 cN/dtex. If the storage modulusat not lower than 30° C. and not higher than 80° C. exceeds 1500cN/dtex, when the braid is used as a fishing line, even slightdisturbance is transmitted as stress to fingers and it becomes difficultto distinguish a bite of fish from noise, and therefore it is notpreferable. In addition, the fishing line gives rough and stiff feelingwhen wound on a reel due to loss of the ductility, and therefore it isnot preferable. When the braid is used as a blind cord, the ductility islost owing to the high storage modulus, and therefore it is notpreferable.

At least one polyethylene fiber constituting the braid product has ashrinkage stress of preferably not more than 5.0 cN/dtex at not lowerthan 30° C. and not higher than 80° C., when measured by athermo-mechanical analyzer (TMA) after the polyethylene fiber isun-braided from the braid. The shrinkage stress is more preferably notmore than 0.8 cN/dtex, and furthermore preferably not less than 0.001cN/dtex and not more than 0.7 cN/dtex. At least one polyethylene fiberconstituting the braid product has a thermal shrinkage percentage ofpreferably not less than 0.45% and not more than 5.00% at 80° C. for 240hours after the polyethylene fiber is un-braided from the braid. Thethermal shrinkage percentage is more preferably not less than 0.48% andnot more than 4.95%, and furthermore preferably not less than 0.50% andnot more than 4.70%.

In the braid of the present invention, a specific gravity is preferablynot less than 0.8 g/cm³ and not more than 2.0 g/cm³. The specificgravity is more preferably not less than 0.85 g/cm³ and not more than1.9 g/cm³, and furthermore preferably not less than 0.90 g/cm³ and notmore than 1.7 g/cm³. If the specific gravity is less than 0.8 g/cm³,when the braid is used as a fishing line, the fishing line tends to beaffected by tide, and therefore it is not preferable.

The braid of the present invention is preferable to have a loop strengthretention rate of not less than 15% when measured in accordance with JISL-1013. The loop strength retention rate is preferably not less than 20%and more preferably not less than 25%. The loop strength retention ratecan be calculated according to the equation below:

Loop strength retention rate (%)=100×(loop strength)/(tensile strength)

The characteristic of the polyethylene fiber obtained in the presentinvention are measured and evaluated as follows.

(1) Intrinsic viscosity

Decalin at a temperature of 135° C. was used to obtain various dilutedsolutions, and specific viscosities of the diluted solutions weremeasured by Ubbelohde capillary viscometer. An intrinsic viscosity wasdetermined based on extrapolated points to an originating point of astraight line obtained by least squares approximation of the viscositiesplotted against concentrations. When the measurement was performed, asample was divided or cut into portions each having a length of about 5mm, and 1 mass % of an antioxidant (trade name: “YOSHINOX BHT”,manufactured by Yoshitomi Pharmaceutical Co., Ltd.) relative to apolymer was added, and stirred and dissolved at 135° C. for 24 hours, toprepare measurement solutions.

(2) Fineness

Each sample was cut in 10 cm size at 5 different positions, the weightsthereof were measured, and an average value of the weights wascalculated to determine fineness.

(3) Tensile Strength, Elongation, and Elastic Modulus

A measurements was carried out in accordance with JIS L1013 8.5.1.Regarding tensile strength and elastic modulus, a strain-stress curvewas obtained, under the condition that a length of a sample was 200 mm(a length between chucks), and an elongation speed was 100%/min, anambient temperature was 20° C., and a relative humidity was 65%, byusing a “TENSILON Universal Material Testing Instrument” manufactured byORIENTEC Co., LTD. A tensile strength (cN/dtex) and an elongation (%)were calculated based on a stress and an elongation at breaking point,and an elastic modulus (cN/dtex) was calculated from the tangent lineproviding a maximum gradient on the curve in the vicinity of theoriginating point. At this time, an initial load applied to the sampleat the measurement was one tenth of fineness. An average of valuesobtained in ten measurements was used for each case.

(4) Measurement of Thermal Shrinkage Stress

A thermal stress stain measurement apparatus (TMA/SS120C) manufacturedby Seiko Instruments Inc. was used for the measurement. An initial loadof 0.01764 cN/dtex was applied to a fiber having a length of 20 mm, anda temperature was increased from room temperature (20° C.) to themelting point at a temperature rising speed of 20° C./min to obtainthermal stress measurement results. A thermal shrinkage stress from 30°C. to 80° C. was measured from the measurement results.

(5) Specific Gravity

A specific gravity of the fiber was measured by using a density gradienttube method.

(Production of Density Gradient Tube)

Water was used as a heavy liquid, and isopropyl alcohol was used as alight liquid. While the light liquid was continuously and graduallymixed with the heavy liquid, they were poured into a glass tube havingscale marks. The heavy liquid was in the bottom portion of the glasstube, and a proportion of the light liquid was increased toward theupper portion of the glass tube. Thus, a density gradient tube wasproduced. The density gradient tube was then put into a constanttemperature oven having a temperature of 30° C.±0.1° C.

Next, five or more glass balls (having specific gravities different fromeach other) of which the specific gravities were known were carefullyput into the density gradient tube having been produced, and they wereallowed to stand as they were for one day. Thereafter, a distancebetween each glass ball and the liquid level was measured, and a graph(a calibration curve) in which the obtained distances were representedby the vertical axis, and values of the specific gravities of the glassballs were represented by the horizontal axis, was made. The graphrepresented a straight line, and it was confirmed that a correctspecific gravity solution was obtained.

(Measurement of Specific Gravity)

Fiber (braid) samples (the lengths of the samples: 6 to 8 mm) were putinto the density gradient tube having been produced as described above.Positions of each fiber sample from the liquid level were measuredimmediately after and five hours after the fiber sample was put into thedensity gradient tube. A value of the specific gravity at the positionof each sample was obtained by using the calibration curve having beenmade when the density gradient tube was produced.

(6) Thermal Shrinkage Measurement

A measurement was carried out in accordance with JIS L1013 8.18.2 drythermal shrinkage percentage (b) method. Fiber samples and braid samplesto be measured were each cut into a size of 70 cm, and positions distantfrom both ends, respectively, by 10 cm, were marked so as to show that alength of each sample was 50 cm. Next, the fiber samples and the braidsamples were hung on so as to prevent a load from being applied thereto,and the fiber samples and the braid samples in this hanging state wereheated at a temperature of 80° C. in a hot air circulating type heatingfurnace for 240 hours. Thereafter, the fiber samples were taken out ofthe heating furnace, and gradually cooled down sufficiently to roomtemperature. Thereafter, a length between the positions which had beenmarked on each fiber sample and braid sample at the beginning, wasmeasured. The thermal shrinking percentage can be obtained by using thefollowing equation.

Thermal shrinking percentage (%)=100×(lengths of fiber sample and braidsample before heating−lengths of fiber sample and braid sample afterheating)/(lengths of fiber sample and braid sample before heating)

An average of values obtained in two measurements was used for eachcase.

(7) Storage Modulus at Not Lower than 30° C. and Not Higher than 80° C.

A solid viscoelasticity measurement apparatus (DMA Q800) manufactured byT. A. Instruments was used. The measurement condition was such that alength of a measurement sample was 10 mm. In the measurement, in orderto prevent slipping between the fiber sample and chucks of the apparatusand separation of monofilaments after an original filament wasun-braided from a braid, both ends of the fiber sample was eachsandwiched by a cardboard by using an adhesive and a double-faced tape.Thus, the cardboards were placed between the fiber sample and the chucksof the apparatus in the measurement, thereby enabling reduction ofslipping at the chucks of the apparatus and separation of monofilamentsin the case of fiber. The measurement start temperature was set to −130°C., the measurement end temperature was set to 150° C., and atemperature rising rate was set to 1.0° C./min. A strain was set to0.04%, an initial load at the start of the measurement was set to 0.1cN/dtex, and force track was set to 350%. Further, a measurementfrequency was 11 Hz. “T. A. Universal Analysis” manufactured by T. A.Instruments was used for data analysis. Storage modulus at not lowerthan 30° C. and not higher than 80° C. was measured under theabove-mentioned conditions.

(8) Tensile Strength Retention Rate Under Environment of 80° C. for 240Hours

After treated at a temperature of 80° C. in a heating furnace for 240hours, each braid sample was cooled in a room at temperature of 20±2° C.for 24 hours or longer to measure strength in the same manner as in (3)above. A tensile strength retention rate was calculated according to thefollowing equation.

Physical property retention rate under an environment of 80° C. for 240hours (%)=100×(tensile strength after treatment at 80° C. for 240hours/tensile strength before treatment)

(9) Concentration of Residual Solvent

A concentration of a residual solvent in a fiber sample was measured byusing a gas chromatography (manufactured by SHIMADZU CORPORATION). 10 mgof a sample fiber was set in a glass insert in a gas chromatographyinjector. The injector was heated to a temperature equal to or higherthan the boiling point of the solvent, and the solvent vaporized due tothe heating was introduced into a column by nitrogen purge. Thetemperature of the column was set to 40° C., and the solvent was trappedfor 5 minutes. Next, the temperature of the column was increased to 80°C., and the measurement was then started. A concentration of theresidual solvent was obtained from an obtained peak.

EXAMPLES

Hereinafter, the present invention will be described specifically withreference to examples, but the invention is not limited to theseexamples.

Example 1

A dispersion containing ultra high molecular weight polyethylene havingan intrinsic viscosity of 17.0 dL/g and a weight average molecularweight of 2,800,000 and decalin was adjusted so as to have apolyethylene concentration of 9.0 wt %. This dispersion was convertedinto a solution at 205° C. by an extruder, and the obtained polyethylenesolution was discharged from a spinneret having 30 holes each having anorifice diameter of φ1.0 mm at a nozzle surface temperature of 180° C.at 2.0 g/min of through put at single hole. Discharged filaments weredeformed 16 times until the filaments were solidified, and then cooledin a cooling water bath at 30° C. to obtain undrawn filaments. The timerequired for the deformation is 0.1 minutes. Successively, the undrawnfilaments were drawn 4.0 times while being dried by hot air at 120° C.The resulting filaments were drawn 4.1 times by hot air at 150° C. for40 seconds, quick quenched by using water baths continuously, and thenthe drawn filaments were immediately wound up. In this case, the coolingspeed to 50° C. was 20° C./sec. A temperature at the time of winding upthe drawn filaments was set to 30° C. and a tension was set to 0.10cN/dtex. These drawing steps were carried out continuously.

Four of the undrawn filaments were braided to produce a braid, and thebraid was subjected to heat treatment at 144° C. and a tension of 1.900cN/dtex for 4 minutes. In this case, the braid was subjected to the heattreatment while being drawn 2.1 times. After the heat treatment, theheat-treated braid was wound up at 32° C. The physical properties of theobtained fiber and braid are shown in Table 1 and Table 2.

Example 2

A braid was obtained in the same manner as in Example 1, except that thetime until the filaments after drawing were put in the water bath forquick quenching was shortened, the cooling speed after drawing waschanged to 50° C./sec, the winding up tension of the fiber was changedto 0.18 cN/dtex, the tension at the time of the heat treatment afterbraid formation was changed to 2.05 cN/dtex, the draw ratio at the timeof the heat treatment for braid was changed to 2.4 times, and theheat-treated braid was wound up at 40° C. after the heat treatment. Thephysical properties of the obtained fiber and braid are shown in Table 1and Table 2.

Example 3

A braid was obtained in the same manner as in Example 1, except that thepolymer concentration was changed to 8 wt %, the deformationmagnification and the deformation time at the time of spinning werechanged to 24 times and 0.3 minutes, respectively, the draw ratio in thefirst stage was changed to 4.5 times, the draw ratio in the second stagewas changed to 4.5 times, the drawing deformation time was changed to 38seconds, the tension and the magnification at the time of the heattreatment after braid formation were changed to 3.95 cN/dtex and 1.8times, respectively. The physical properties of the obtained fiber andbraid are shown in Table 1 and Table 2.

Example 4

A braid was obtained in the same manner as in Example 1, except thatcooling of the fiber after spinning and drawing was carried out using aroller at a cooling speed of 150° C./sec, and the heat treatmentconditions after the braid formation were changed as follows: the heattreatment temperature was 149° C., the heat treatment time was 6minutes, the tension at the time of the heat treatment was 2.10 cN/dtex,and the draw ratio at the time of the heat treatment was 1.9 times. Thephysical properties of the obtained fiber and braid are shown in Table 1and Table 2.

Example 5

A braid was obtained in the same manner as in Example 1, except thatultra high molecular weight polyethylene having an intrinsic viscosityof 12.0 dL/g and a weight average molecular weight of 1,600,000 wasused, the deformation magnification in the spinning step was changed to20 times, the draw ratio in the first stage was changed to 3.0 times,the drawing temperature in the second stage was changed to 145° C., thedraw ratio was changed to 3.5 times, the deformation speed was changedto 0.01 sec⁻¹, the time required for drawing in the second stage waschanged to 2 minutes, cooling of the fiber after spinning and drawingwas carried out using a roller at a cooling speed of 150° C./sec, andthe heat treatment conditions after the braid formation were changed asfollows: the heat treatment temperature was 140° C., the heat treatmenttime was 2 minutes, the tension at the time of the heat treatment was1.30 cN/dtex, and the draw ratio at the time of the heat treatment was1.8 times. The physical properties of the obtained fiber and braid areshown in Table 1 and Table 2.

Example 6

A braid was obtained in the same manner as in Example 1, except thatultra high molecular weight polyethylene having an intrinsic viscosityof 12.0 dL/g and a weight average molecular weight of 1,600,000 wasused, paraffin was used as the solvent, and the polymer concentrationwas changed to 11.0 wt %; after the spinning step, hexane was used toremove the solvent, followed by drying; in the drawing step, the drawingtemperature and the draw ratio in the first stage were changed to 80° C.and 1.3 times, the drawing temperature and the draw ratio in the secondstage were changed to 130° C. and 3.5 times, the drawing temperature andthe draw ratio in the third stage were changed to 150° C. and 2.8 times,the deformation speed in the third stage was changed to 0.018 sec⁻¹, andthe time required for drawing in the third stage was changed to 2minutes; cooling of the fiber after spinning and drawing was carried outusing a roller at a cooling speed of 100° C. /sec, and the fiber waswound up at a winding tension of 0.06 cN/dtex and a temperature atwinding of 40° C.; and the heat treatment conditions after the braidformation was changed as follows: the heat treatment temperature was152° C., the tension at the time of the heat treatment was 4.10 cN/dtex,and the draw ratio at the time of the heat treatment was 5.5 times. Thephysical properties of the obtained fiber and braid are shown in Table 1and Table 2.

Comparative Example 1

A dispersion containing ultra high molecular weight polyethylene havingan intrinsic viscosity of 17.0 dL/g and a weight average molecularweight of 2,800,000 and decalin was adjusted so as to have apolyethylene concentration of 9.0 wt %. This dispersion was convertedinto a solution at 205° C. by an extruder, and the obtained polyethylenesolution was discharged from a spinneret having 30 holes each having anorifice diameter of φ1.0 mm at a nozzle surface temperature of 180° C.at 2.0 g/min of through put at single hole. Discharged filaments weredeformed 16 times until the filaments were solidified, and then cooledin a cooling water bath at 30° C. to obtain undrawn filaments. The timerequired for the deformation is 0.1 minutes. The undrawn filaments werecontinuously drawn 4.0 times while being dried by hot air at 120° C. Theresulting filaments were drawn 4.1 times by hot air at 150° C. for 40seconds, quick quenched by using water baths continuously, and then thedrawn filaments were immediately wound up. In this case, the coolingspeed to 50° C. was 1.5° C./sec. A temperature at the time of winding upthe drawn filaments was set to 30° C. and a tension was set to 0.10cN/dtex. Four of the undrawn filaments were braided to produce a braid,and the braid was subjected to heat treatment at 60° C. and a tension of0.004 cN/dtex for 4 minutes. In this case, the braid was subjected tothe heat treatment while being drawn 2.1 times. After the heattreatment, the heat-treated braid was wound up at 32° C. The physicalproperties of the obtained fiber and braid are shown in Table 1 andTable 2.

Comparative Example 2

A braid was obtained in the same manner as in Comparative Example 1,except that the cooling speed of the fiber to 50° C. was changed to20.0° C./sec after the drawing step, four of the undrawn filaments werebraided to produce a braid, and the braid was subsequently subjected toheat treatment at 120° C. with a tension of 0.004cN/dtex for 35 minutes.The physical properties of the obtained fiber and braid are shown inTable 1 and Table 2.

Comparative Example 3

A braid was obtained in the same manner as in Comparative Example 1,except that the cooling speed of the fiber was changed to 520° C./secafter the drawing step, four of the undrawn filaments were braided toproduce a braid, and the braid was subsequently drawn 2.1 times at 150°C. and at a tension of 1.90 cN/dtex. In this case, the braid wassubjected to heat treatment while being drawn 2.1 times. The physicalproperties of the obtained fiber and braid are shown in Table 1 andTable 2.

Comparative Example 4

Without using a solvent, high density polyethylene having an intrinsicviscosity of 2 dL/g and a weight average molecular weight of 130,000 wasmelted at 285° C. by an extruder, and the polyethylene solution wasdischarged from a spinneret having 30 holes each having an orificediameter of 0 0.5 mm at a nozzle surface temperature of 280° C. at 0.5g/min of through put at single hole. Discharged filaments were deformed130 times until the filaments were solidified, and then cooled bycooling air blow at 30° C. to obtain undrawn filaments. The timerequired for the deformation is 0.3 minutes. The undrawn filaments werecontinuously drawn 2.0 times while being dried by hot air at 80° C. Theresulting filaments were drawn 5.0 times by hot air at 100° C. for 30seconds, quick quenched by using water baths continuously, and then thedrawn filaments were immediately wound up. In this case, the coolingspeed to 50° C. was 520° C./sec. A temperature at the time of winding upthe drawn filaments was set to 30° C. and a tension was set to 0.10cN/dtex. Four of the undrawn filaments were braided to produce a braid,and the braid was subjected to heat treatment at 80° C. and a tension of0.008 cN/dtex for 4 minutes. In this case, the braid was subjected tothe heat treatment while being drawn 2.1 times. After the heattreatment, the heat-treated braid was wound up at 32° C. The physicalproperties of the obtained fiber and braid are shown in Table 1 andTable 2.

Comparative Example 5

Without using a solvent, high density polyethylene having an intrinsicviscosity of 1.5 dL/g and a weight average molecular weight of 95,000was melted at 280° C. by an extruder, and the polyethylene solution wasdischarged from a spinneret having 30 holes each having an orificediameter of 0 0.5 mm at a nozzle surface temperature of 280° C. at 0.5g/min of through put at single hole. Discharged filaments were deformed130 times until the filaments were solidified, and then cooled bycooling air blow at 30° C. to obtain undrawn filaments. The timerequired for the deformation is 0.3 minutes. The undrawn filaments werecontinuously drawn 2.0 times while being dried by hot air at 80° C. Theresulting filaments were drawn 5.0 times by hot air at 100° C. for 30seconds, quick quenched by using water baths continuously, and then thedrawn filaments were immediately wound up. In this case, the coolingspeed to 50° C. was 520° C./sec. A temperature at the time of winding upthe drawn filaments was set to 30° C. and a tension was set to 0.10cN/dtex. Four of the undrawn filaments were braided to produce a braid,and the braid was subjected to heat treatment at 80° C. and a tension of0.008 cN/dtex for 4 minutes. In this case, the braid was subjected tothe heat treatment while being drawn 2.1 times. After the heattreatment, the heat-treated braid was wound up at 32° C. The physicalproperties of the obtained fiber and braid are shown in Table 1 andTable 2.

TABLE 1 unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6

[dL g] 17 17 17 17 12 17

[

] 2,

00,000

400,000 2,

,000

00,000 1,

1,

0,000

9.0 8.0 8.0 9.0 9.0 11.0

[° C.]

100

[Mpa]

5.0 5.0 5.0 5.0 5.0

1.0 1.0 1.0 1.0 1.0 1.0

[° C.] 110

1

100 100 100

[

] 2.0 2.0 2.0 2.0 2.0 2.0

[

] 16 16

1

[

] 0.1 0.1

0.1

[° C.] 130 120 1

1

0 1

[

] 4.0 4.0 4

4.0

1

[° C.] 150 1

0 1

0 5 110 150

4.1 4.3 4.5 4.1 3.2 3.5

[° C.] 150

2

[

] 0.010 0.0

0.018 0.018 0.0

0.0

] 10.4 10.4 20.1

1

1

[° C.] 150 150 150 150

150

[min]

min

min

min

min

min

min

[

]

20.0 150.0 150.0 150.0

0.10

0.10

[° C.]

0

0

0

0

40 property

[

] 16.0

16.0 16.0 11.5 11.0

[

]

21.1

[

] 12

1251 1

1

5

[

] 0

0

0

0.

0.01

[

] 0

0

0.51 0.01 2

0

[° C.]

1

1

118 1

Comparative Comparative Comparative Comparative Comparative unit Example1 Example 2 Example 3 Example 4 Example 5

[dL g] 17 17 17 2 15

[

] 2,

0,000 2,

0,000 2,

0,000 1

0,000 95,000

— —

9.0 9.0 9.0 100.0 100.0

[° C.]

100 100 20 20

[Mpa] 5.0 5.0 5.0 35.0 35.0

1.0 1.0 1.0 1.0 0.5

[° C.] 1

1

2

2

[

] 2.0 2.0 2.0 0.1 0.5

[

] 1

1

1

1

1

[

] 0.1 0.1 0.1 0.1 0.3

[° C.] 1

1

1

0

0

[

] 4.0 4.0 4.0 1.0 2.0

[° C.] 1

0

0 1

0 100 100

4.1 4.1 4.1 3.5 2.0

[° C.]

[

] 0.0

0.0

0.0

0.

] 1

10

1

1

1

[° C.] 1

2

1

100 100

[min]

min

min

min

min

min

[

] 1.5 20.0 520.0

520.0

2.10 0.10 [° C.] 30 30 30 30 30 property

[

]

35.0

1.8 1.7

[

] 19

34.2 34.4 12.5 8.2

[

] 4

1

131.5 4

[

] 0

1

0

4

[

]

0.5

1.25

[° C.]

1

1

9

indicates data missing or illegible when filed

TABLE 2 unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6

production method heat treatment temperature (° C.) 144 144 144 149 140152 heat

 time [min] 4 min 4 min 4 min

min 2 min 4 min

 at the time of heat

[

] 1.960 2.050 3.950 3.100 1300 4.100

 ratio [times] 2.1 2.4 1.8 1.0 1.8 5.5

-up temperature (° C.) 32

3

2

2 32 property tensile strength [

] 22.8 24.9 27.1 34.8 12.5 23.8

 at the time of 1%

[

] 10 10.3 11.3 10 6.3 10.5 elastic

[

] 855

1011

260 1151 loop strength

 rate [%] 38 39 38 38 43 43 specific gravity [

] 0.060 0.960 0.970 0.960 0.970 0.960 the number of

 fiber 4 4 4 4 4 4

 with resin olefin olefin olefin olefin olefin olefin unevenness of

 in

 direction [%] 5.3 5.2 1.3 5.3 6.9 8.5 storage

 at no longer than 30° C. [%] 85

5 86 90 75 81 and not higher than 80° C. thermal shrinkage stess at30-80° C. [

] thermal shrinkage at 80° at 240 hours [%] 1.22 1.20 1.20 1.20 0.951.66 tensile strength

 rate at 80° C. [%] 95 101 98 104 86 95 for 240 hours property ofstorage

 at not lower than 30° C. [%] 87 86 8

89 72

2 fiber after and not higher than 80° C. the braid is Thermal shrinkage

 30-80° C. [

] 0.43 0.42 0.45 0.25 0.59 0.51 un-braided Thermal thickness at 80° C.for 80° [%] 1.24 1.36 1.28 1.09 4.13 1.36 for 24 hours ComparativeComparative Comparative Comparative Comparative unit Example 1 Example 2Example 3 Example 4 Example 5

production method heat treatment temperature (° C.) 60 120 150 80 80heat

 time [min] 4 min 35 min 4 min 4 min 4 min

 at the time of heat

[

] 0.004 0.004 1.900 0.008 0.008

 ratio [times] 2.1 2.1 2.1 2.1 2.1

-up temperature (° C.) 32 32 32 32 32 property tensile strength [

] 7

11.0 23.3 7.5 7.2

 at the time of 1%

[

] 6.4 6.4 11.2 1.4 0.3 elastic

[

] 140 145 805 140 130 loop strength

 rate [%] 35 40 35 41 33 specific gravity [

] 0.960 0.96 0.96 0.960 0.950 the number of

 fiber 4 4 4 4 4

 with resin olefin olefin olefin olefin olefin unevenness of

 in

 direction [%] 22.3 13.

19.3 2.3 4.1 storage

 at no [%] 35

1

3 38 36 longer than 30° C. and not higher than 80° C. thermal shrinkagestess at 30-80° C. [

] thermal shrinkage at 80° at 240 hours [%] 1.3

0.10

.65 8.86 8.92 tensile strength

 rate at 80° C. [%] 61 65 7

65 65 for 240 hours property of storage

 at not lower than 30° C. [%] 36

3 85 37 37 fiber after and not higher than 80° C. the braid is Thermalshrinkage

 30-80° C. [

] 0.005 0.004 5.11 0.21 0.20 un-braided Thermal thickness at 80° C. for80° [%] 0.24 0.20 8.44 8.95 5.98 for 24 hours

indicates data missing or illegible when filed

INDUSTRIAL APPLICABILITY

The braid of the present invention is suitable not only for long-termstorage but also for long-term use application, and exhibits excellentperformance for use as fishing lines, various kinds of interior cordsand nets such as blind cords, pleated cords, pleated screen door cords,curtain chords and shading screens, all of which being required formoving up and down and opening and closing, fenders, surgical sutures,fastening filaments for meat, safety gloves, safety ropes, ropes forfishery industries, finishing ropes, archery chords, etc. The braid ofthe invention is further widely usable in industrial application notonly for use as the above-mentioned molded products but also as basematerials for collecting organic and inorganic matters by makingcomposites with various kinds of materials as well as water-retainingbase materials.

1. A braid comprising a polyethylene fiber or polyethylene tape whichhas an intrinsic viscosity [η] of not less than 5.0 dL/g and not morethan 30 dL/g and contains not less than 90% of ethylene as a repeatingunit thereof, wherein a thermal shrinkage percentage is not less than0.45% and not more than 8% under an environment of 80° C. for 240 hours.2. A braid comprising a polyethylene fiber or polyethylene tape whichhas an intrinsic viscosity [η] of not less than 5.0 dL/g and not morethan 30 dL/g and contains not less than 90% of ethylene as a repeatingunit thereof, wherein a tensile strength retention rate is not less than85% and not more than 115% under an environment of 80° C. for 240 hours.3. The braid according to claim 1, wherein a stress at the time of 1%elongation is not less than 0.5 cN/dtex and not more than 20 cN/dtex. 4.The braid according to claim 1, wherein a thermal shrinkage stress atnot lower than 30° C. and not higher than 80° C. is not more than 5.0cN/dtex when measured by a thermo-mechanical analyzer (TMA).
 5. Thebraid according to claim 1, wherein a loop strength retention rate isnot less than 15% when measured in accordance with JIS L-1013.
 6. Thebraid according to claim 1, wherein the braid is constituted from notless than 3 yarns and at least one yarn constituting the braid is apolyethylene fiber.
 7. A braid constituted from at least onepolyethylene fiber having an intrinsic viscosity [η] of not less than5.0 dL/g and not more than 30 dL/g, comprising not less than 90% ofethylene as a repeating unit thereof, and having a storage modulus atnot lower than 30° C. and not higher than 80° C. of not less than 70cN/dtex when measured by a solid viscoelasticity measurement apparatusafter the braid is un-braided.
 8. A braid constituted from at least onepolyethylene fiber having an intrinsic viscosity [η] of not less than5.0 dL/g and not more than 30 dL/g, comprising not less than 90% ofethylene as a repeating unit thereof, and having a thermal shrinkagestress at not lower than 30° C. and not higher than 80° C. of not morethan 5.0 cN/dtex when measured by a thermo-mechanical analyzer (TMA)after the braid is un-braided.
 9. The braid according to claim 1,wherein a specific gravity is not less than 0.80 and not more than 2.0and an average tensile strength is not less than 8 cN/dtex and not morethan 50 cN/dtex.
 10. The braid according to claim 9, wherein the braidis colored.
 11. The braid according to claim 1, wherein the braid isdrawn at a draw ratio of not less than 1.05 times and not more than 15.0times at not higher than 160° C. after braid production.
 12. A fishingline using the braid according to claim
 1. 13. A rope using the braidaccording to claim
 1. 14. A method for producing a braid, comprisingspinning a polyethylene which has an intrinsic viscosity [η] of not lessthan 5.0 dL/g and not more than 30 dL/g and contains not less than 90%of ethylene as a repeating unit thereof, drawing the polyethylene attemperature of not lower than 80° C., cooling the drawn filament at acooling speed of not lower than 3° C./sec, winding up the obtained drawnfilament at a tension of 0.001 to 7 cN/dtex to prepare a polyethylenefiber, twisting the polyethylene fiber if necessary, and adjusting, in asubsequent braid production step, a time for heating the polyethylenefiber constituting the braid to a temperature of not lower than 70° C.to not longer than 30 minutes and a tension applied to the polyethylenefibers during the heating to not less than 0.005 cN/dtex and not morethan 15 cN/dtex.